Apolipoprotein A-IV is a lipid binding protein found in the intestine, which plays a role in the absorption of dietary fat. A genetic variation, apo A-IV-2, has been found to affect how much dietary cholesterol changes cholesterol in the blood. The purpose of this project was to examine the mechanism by which this variant gene works. Research subjects carrying the A-IV-2 gene, and a control group of subjects who do not, were studied to measure how much cholesterol they absorb from the diet. The subjects were fed diets containing known amounts of cholesterol but different amounts and types of fat.